Thermoplastic Polyurethanes

ABSTRACT

Thermoplastic polyurethanes are obtainable by reacting (a) isocyanates with (b1) polyesterdiols having a melting point greater than 150-C, (b2) polyetherdiols and/or polyesterdiols, each having a melting point of less than 150-C and a molecular weight of from 501 to 8 000 g/mol, and, if required, (c) diols having a molecular weight of from 62 to 500 g/mol.

The present invention relates to thermoplastic polyurethanes obtainableby reacting (a) isocyanates with (b1) polyesterdiols having a meltingpoint greater than 150° C. preferably from 151 to 260° C., particularlypreferably from 165 to 245° C., (b2) polyetherdiols and/orpolyesterdiols, each having a melting point of less than 150° C.,preferably from 0 to 149° C., and a molecular weight of from 501 to 8000 g/mol, and, if required, (c) diols having a molecular weight of from62 to 500 g/mol, The present invention furthermore relates to a processfor the preparation of thermoplastic polyurethanes and productscontaining the novel thermoplastic polyurethanes.

Thermoplastic elastomers are based on a standard structural principle,regardless of their chemical composition. They are block copolymers inwhich hard blocks are connected to soft blocks in a polymer chain. Hardblocks are to be understood as meaning polymer segments whose softeningtemperature—glass transition temperature or crystallite melting point—isfar above the temperature of use, Soft blocks are polymer segmentshaving softening temperatures well below the temperature of use,preferably less than 0° C. The hard blocks form physical networks whichcan be reversibly cleaved during the thermoplastic processing andreformed on cooling.

Typical examples are styrene/butadiene block copolymers having hardpolystyrene blocks (glass transition temperature about 105° C.) and softpolybutadiene blocks (glass transition temperature about −90° C.) orthermoplastic polyurethanes (TPU). The latter product group has, as asemicrystalline hard phase, the reaction product of an organicdiisocyanate with a low molecular weight diol and, as an amorphous softphase, the reaction product of an organic diisocyanate with apolyesterdiol or a polyetherdiol having molecular weights of, usually,from 500 to 5 000 g/mol.

The solidification behavior of this semicrystalline polyurethane hardphase is however very variable and can easily be influenced,deteriorations generally occurring. For example, an increase in theindex (ratio of moles of isocyanate to moles of OH-containingcomponents) to the range of from 1.05 to 1.20 has a very adverse effect,as does the addition of other polymers. The conventional preparationprocesses, such as belt and extruder processes, also lead, with the sameformulation, to TPU having substantially different crystallizationbehavior. However, in all processing methods, whether injection moldingor extrusion, a constant and rapid solidification rate is a substantialfactor influencing the uniform quality of the shaped articles,properties such as hardness, strength, rigidity and heat distortionresistance, and the cost-efficiency of the production.

A wide range of efforts has been made to compensate this disadvantageousbehavior of the TPU. Apart from the addition of nucleating agents, e.g.finely divided talc, attempts have also been made to achieveimprovements by adding other, rapidly crystallizing polymers.Thermoplastic, semicrystalline polyesters were particularly frequentlyused, among these preferably polybutylene terepthalate, owing to itsmelting range of from 220 to 230° C. which very well matches thecustomary TPU processing temperatures.

Thus, DE-A 26 46 647 describes the compounding of prepared, highmolecular weight polyesters and high molecular weight TPU insingle-screw or twin-screw extruders. EP-A 334 186 and DE-A 41 13 891disclose the compounding of high molecular weight polyesters and TPUmonomer components DE-A 41 28 274 describes the addition of up to 5% ofdiisocyanate in excess for such processes. For an improvement in thecompatibility, EP-A 656 397 describes the use of a TPU having an indexgreater than 1.16 and admixture with high molecular weight polyester.These processes lead to two-phase polymer mixtures, the polymercomponent, when present in amounts greater than 50%, having particlesizes of from 10 to 50 mm or <5 mm with the use of additionaldiisocyanate. Such molding materials are said to have higher strength,rigidity and heat distortion resistance than an unmodified TPU. On theother hand, the fact that a substantial reduction in the solidificationrate occurs in particular on addition of diisocyanate in excess is verydisadvantageous.

EP-A 102 115 and EP-A 846 712 describe the reaction of polyalkyleneterephthalates with aliphatic polyesters to give blockcopolyester-esters, which in turn are then reacted with organicdiisocyanates. The polycondensation of dimethyl terephthalate,butanediol and polyetherdiol and the subsequent reaction of thepolyester with further polyetherdiol and diisocyanates to give a highmolecular weight product are described in WO 99/51656. The long reactiontimes and the high temperatures, which easily lead to pronounceddiscoloration of the molding materials, are disadvantageous in all theseprocesses.

DE-A 199 39 112 describes the degradation of hard thermoplasticpolyurethanes with low molecular weight diols and the subsequentreaction with isocyanates for the preparation of flexible TPU.

It is an object of the present invention to provide thermoplasticpolyurethanes having improved crystallization behavior of the hard phaseand a very constant and rapid solidification rate during processing.

We have found that this object is achieved by the thermoplasticpolyurethanes described at the outset.

Thermoplastic polyurethanes in which the molar ratio of the diols (c)having a molecular weight of from 62 to 500 g/mol to the component (b2)is less than 0.2, particularly preferably from 0.1 to 0.01, arepreferred.

Thermoplastic polyurethanes in which the polyesterdiols (b1), whichpreferably have a molecular weight of from 1 000 to 5 000 g/mol, havethe following structural unit (I):

where

R1 is a carbon skeleton of 2 to 15 carbon atoms, preferably an alkylenegroup of 2 to 15 carbon atoms and/or a bivalent aromatic radical of 6 to15, particularly preferably 6 to 12, carbon atoms,

R2 is a straight-chain or branched alkylene group of 2 to 8, preferably2 to 6, particularly preferably 2 to 4, carbon atoms, in particular—CH2—CH2— and/or —CH2—CH2—CH2—CH2—,

R3 is a straight-chain or branched alkylene group of 2 to 8, preferably2 to 6, particularly preferably 2 to 4, carbon atoms, in particular—CH2—CH2— and/or —CH2—CH2—CH2—CH2—, and

X is an integer from 5 to 30. In this preferred embodiment, the meltingpoint described at the outset and according to the invention and/or themolecular weight according to the invention relate to the structuralunit (I) shown.

In this document, the term melting point is to be understood as meaningthe maximum of the melting peak of a heating curve which was measuredusing a commercial apparatus (e.g. DSC 7/Perkin-Elmer), preferably a DSCapparatus, and evaluated according to ISO 11357-3.

The molecular weights stated in this document are the number averagemolecular weights in [g/mol].

The novel thermoplastic polyurethanes can preferably be prepared by

-   -   (i) reacting a preferably high molecular weight, preferably        semicrystalline, thermoplastic polyester with a diol (c) and        then    -   (ii) reacting the reaction product from (i) containing (b1)        polyesterdiol having a melting point greater than 150° C. and,        if required, (c) diol together with (b2) polyetherdiols and/or        polyesterdiols, each having a melting point of less than 150° C.        and a molecular weight of from 501 to 8 0000 g/mol, and, if        required, further (c) diols having a molecular weight of from 62        to 500 g/mol with (a) isocyanate, in the presence or absence        of (d) catalysts and/or (e) assistants.

In the reaction (ii), the molar ratio of the diols (c) having amolecular weight of from 62 to 500 g/mol to the component (b2) ispreferably less than 0.2, especially from 0.1 to 0.01.

Whereas the hard phases are provided for the end product by the step(i), by the polyester used in step (i), the soft phases are synthesizedby the use of the component (b2) in step (ii). In the novel technicalprocedure, polyesters having a pronounced, readily crystallizing hardphase structure are melted, preferably in a reaction extruder, and arefirst degraded with a low molecular weight diol to give shorterpolyesters having free terminal hydroxyl groups. Here, the original hightendency of the polyester to crystallize is retained and cansubsequently be utilized for obtaining, in a rapid reaction, TPU havingthe advantageous properties, such as high tensile strength values, lowabrasion values and, owing to the high and narrow melting range, highheat distortion resistances and low compression sets.

Thus, in the novel process, high molecular weight, semicrystalline,thermoplastic polyesters are preferably degraded with low molecularweight diols (c) under suitable conditions in a short reaction time togive rapidly crystallizing polyester diols (b1), which in turn are thenincorporated, with other polyesterdiols and/or polyetherdiols anddiisocyanates, into high molecular weight polymer chains.

The thermoplastic polyester used preferably has, i.e. before thereaction of (i) with the diol (c), a molecular weight of from 15 000 to40 000 g/mol and preferably a melting point greater than 160° C.,particularly preferably from 170 to 260° C.

Generally known, preferably high molecular weight, preferablysemicrystalline, thermoplastic polyesters, for example in granulatedform, can be used as starting material, i.e. as polyester which isreacted in step (i), preferably in the molten state, particularlypreferably at from 230 to 280° C., preferably for from 0.1 to 4 minutes,particularly preferably from 0.3 to 1 minute, with the diol or diols(c). Suitable polyesters are based, for example, on aliphatic□-hydroxycarboxylic acids and/or on aliphatic, cycloaliphatic,araliphatic and/or aromatic dicarboxylic acids, for example lactic acidand/or terephthalic acid, and aliphatic, cycloaliphatic, araliphaticand/or aromatic dialcohols, for example 1,2-ethanediol, 1,4-butanedioland/or 1,6-hexanediol.

Particularly preferably used polyesters are poly-L-lactic acid and/orpolyalkylene terephthalate, for example polyethylene terephthalate,polypropylene terephthalate or polybutylene terephthalate, in particularpolybutylene terephthalate.

The preparation of these esters from said starting materials isgenerally known to a person skilled in the art and is widely described.Suitable polyesters are furthermore commercially available.

The thermoplastic polyester is melted, preferably at from 180 to 270° C.The reaction (i) with the dial (c) is preferably carried out at from 230to 280° C., preferably from 240 to 280° C.

Generally known diols having a molecular weight of from 62 to 500 g/mol,for example those mentioned below, e.g. ethylene glycol,1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,heptanediol, octanediol, preferably 1,4-butanediol and/or1,2-ethanediol, may be used as diol (c) in step (i) for the reactionwith the thermoplastic polyester and, if required, in step (ii).

The weight ratio of the thermoplastic polyester to the diol (c) in step(i) is usually from 100:1.0 to 100:10, preferably from 100:1.5 to100:8.0.

The reaction of the thermoplastic polyester with the diol (c) in thereaction step (i) is preferably carried out in the presence ofconventional catalysts, for example those which are described below.Catalysts based on metals are preferably used for this reaction. Thereaction in step (i) is preferably carried out in the presence of from0.1 to 2% by weight, based on the weight of the diol (c), of catalysts.The reaction in the presence of such catalysts is advantageous forenabling the reaction to be carried out in the available short residencetime in the reactor, for example a reaction extruder.

Examples of suitable catalysts for this reaction step (i) are tetrabutylorthotitanate and/or tin(II) dioctanoate, preferably tin dioctanoate.

The polyesterdiol (b1) as a reaction product from (i) preferably has amolecular weight of from 1 000 to 5 000 g/mol. The melting point of thepolyesterdiol as a reaction product from (i) is preferably from 150 to260° C., particularly preferably from 151 to 260° C., in particular from165 to 245° C., i.e. the reaction product of the thermoplastic polyesterwith the dial (c) in step (i) contains compounds having said meltingpoint which are used in the subsequent step (ii).

As a result of the reaction of the thermoplastic polyester with the diol(c) in step (i), the polymer chain of the polyester is cleaved bytransesterification by the diol (c). The reaction product of the TPUtherefore has free terminal hydroxyl groups and is further processedaccording to the invention in the further step (ii) to give the actualproduct, the TPU.

The reaction of the reaction product from step (i) in step (ii) iseffected, according to the invention, by adding (a) isocyanate (a) and(b2) polyetherdiols and/or polyesterdiols, each having a melting pointof less than 150° C. and a molecular weight of from 501 to 8 000 g/mol,and, if required, further diols (c) having a molecular weight of from 62to 500, (d) catalysts and/or (e) assistants to the reaction product from(i). The reaction of the reaction product with the isocyanate iseffected via the terminal hydroxyl groups formed in step (i). Thereaction in step (ii) is preferably effected at from 190 to 250° C.,preferably for from 0.5 to 5, particularly preferably from 0.5 to 2,minutes, preferably in a reaction extruder, particularly preferably inthe same reaction extruder in which the step (i) was also carried out.For example, the reaction of step (i) can be effected in the firstbarrels of a conventional reaction extruder and the correspondingreaction of step (ii) can be carried out at a downstream point, i.e. indownstream barrels, after the addition of the components (a) and (b2).For example, the first 30 to 50% of the length of the reaction extrudercan be used for step (i) and the remaining 50 to 70% can be employed forstep (ii).

The reaction in step (ii) is preferably effected with an excess of theisocyanate groups relative to the groups reactive toward isocyanates. Inthe reaction (ii), the ratio of the isocyanate groups to the to thehydroxyl groups is from 1:1 to 1.2:1, particularly preferably from1.02:1 to 1.2.1.

The reactions (i) and (ii) are preferably carried out in a generallyknown reaction extruder. Such reaction extruders are described by way ofexample in Werner & Pfleiderer's company publications or in DE-A 2 302564.

The novel process is preferably carried out in such a way that at leastone thermoplastic polyester, e.g. polybutylene terephthalate, is meteredinto the first barrel of a reaction extruder and is melted at,preferably, from 180 to 270° C., especially from 240 to 270° C., a diol(c), e.g. butanediol, and preferably a transesterification catalyst areadded to a downstream barrel, the polyester is degraded by the diol (c)at from 240 to 280° C. to give polyester oligomers having terminalhydroxyl groups and molecular weights of from 1 000 to 5 000 g/mol,isocyanate (a) and (b2) compounds reactive toward isocyanates and havinga molecular weight of from 501 to 8 000 g/mol and, if required, (c)diols having a molecular weight of from 62 to 500, (d) catalysts and/or(e) assistants are metered into a downstream barrel and the synthesis togive the novel thermoplastic polyurethanes is then carried out at from190 to 250° C.

In step (ii), no (c) diols having a molecular weight of from 62 to 500are fed in, with the exception of the (c) diols having a molecularweight of from 62 to 500 which are contained in the reaction product of(i).

The reaction extruder preferably has neutral and/or backward-conveyingkneading blocks and backward-conveying elements in the region in whichthe thermoplastic polyester is melted and preferably screw mixingelements, toothed disks and/or toothed mixing elements in combinationwith backward-conveying elements in the region in which thethermoplastic polyester is reacted with the diol.

Downstream of the reaction extruder, the clear melt is usually fed bymeans of a gear pump to an underwater granulation stage and isgranulated.

The novel thermoplastic polyurethanes have optically clear, single-phasemelts which rapidly solidify and, owing to the semicrystalline hardpolyester phase, form slightly opaque to white opaque moldings. Therapid solidification behavior is a decisive advantage compared withknown formulations and preparation processes for thermoplasticpolyurethanes. The rapid solidification behavior is so pronounced thateven products having hardnesses of from 50 to 60 Shore A can beprocessed by injection molding with cycle times of less than 35 seconds,In extrusion too, for example in the production of blown films, noTPU-typical problems such as adhesion or blocking of the films or tubesoccur.

The amount of the thermoplastic polyester in the end product, i.e. thethermoplastic polyurethane, is preferably from 5 to 75% by weight. Thenovel thermoplastic polyurethanes are particularly preferably productsof the reaction of a mixture containing from 10 to 70% by weight of thereaction product from (i), from 10 to 80% by weight of (b2) and from 10to 20% by weight of (a), the stated weights being based on the totalweight of the mixture containing (a), (b2), (d), (e) and the reactionproduct from (i).

The novel thermoplastic polyurethanes preferably have a hardness of fromShore 45 A to Shore 78 D, particularly preferably from 50 A to 75 D.

The novel thermoplastic polyurethanes preferably have the followingstructural unit (II):

where

R1 is a carbon skeleton of 2 to 15 carbon atoms, preferably an alkylenegroup of 2 to 15 carbon atoms and/or an aromatic radical of 6 to 15carbon atoms,

R2 is a straight-chain or branched alkylene group of 2 to 8, preferably2 to 6, particularly preferably 2 to 4, carbon atoms, in particular—CH2—CH2— and/or —CH2—CH2—CH2—CH2—,

R3 is a straight-chain or branched alkylene group of 2 to 8, preferably2 to 6, particularly preferably 2 to 4, carbon atoms, in particularCH2—CH2— and/or —CH2—CH2—CH2CH2—,

R4 is a radical which arises from the use of polyetherdiols and/orpolyesterdiols, each having molecular weights of from 501 to 8 000g/mol, as (b2), or from the use of alkanediols of 2 to 12 carbon atoms,

R5 is a carbon skeleton of 2 to 15 carbon atoms, preferably an alkylenegroup of 2 to 15 carbon atoms and/or a bivalent aromatic radical of 6 to18, particularly preferably 6 to 15, carbon atoms,

X is an integer from 5 to 30 and

n and m are each an integer from 5 to 20.

R1, R2 and R3 are defined by the reaction product of the thermoplasticpolyester with the diol (c) in (i), R4 is defined by the startingcomponents (b2) and, if required, (c) and R5 is defined by theisocyanate used.

The novel product of step (ii), i.e. the TPU, can be extruded, cooledand granulated.

The processing of TPU prepared according to the invention to give thedesired films, fibers, shaped articles, claddings in automobiles,rollers, seals, cable plugs, bellows, tubes, cable sheaths, trailingcables, belts or damping elements, in particular films, can be effectedby conventional methods, for example injection molding, extrusion,spinning process or sinter process, which is also known as a powderslush process.

The components (a), (b2), (c), (d) and/or (e) usually used in thepreparation of the TPU are to be described below by way of example:

a) Organic isocyanates (a) used are conventional aliphatic,cycloaliphatic, araliphatic and/or aromatic isocyanates, preferablydiisocyanates, for example tri-, tetra-, penta-, hexa- or hepta- and/oroctamethylene diisocyanate, 2-methylpentamethylene 1,5-diisocyanate,2-ethylbutylene 1,4-diisocyanate, pentamethylene 1,5-diisocyanate,butylene 1,4-diisocyanate,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophoronediisocyanate, IPDI), 1,4- and/or 1,3-bis(isocyanatomethyl)cyclohexane(HXDI), cyclohexane 1,4-diisocyanate, 1-methylcyclohexane 2,4- and/or2,6-diisocyanate, dicyclohexylmethane 4,41-, 2,4′- and/or2,2′-diisocyanate, diphenylmethane 2,2′-, 2,4′- and/or 4,4′-diisocyanate(MDI), naphthylene 1,5-diisocyanate (NDT), tolylene 2,4- and/or2,6-diisocyanate (TDI), diphenylmethane diisocyanate, dimethylbiphenyl3,3′-diisocyanate, diphenylethane 1,2-diisocyanate and/or phenylenediisocyanate, preferably diphenylmethane 2,2′-, 2,4′- and/or4,4′-diisocyanate (MDI) and/or hexamethylene diisocyanate (HDI).

b) Those compounds (b2) reactive toward isocyanates which are used inaddition to the novel polyesterdiols (b1) are, for example, polyhydroxycompounds, also referred to as polyols, having molecular weights of from501 to 8 000, preferably from 700 to 6 000, in particular from 800 to 4000, and preferably an average functionality of from 1.8 to 2.6,preferably from 1.9 to 2.2, in particular 2. The term functionality isto be understood in particular as meaning the number of active hydrogenatoms, in particular hydroxyl groups. Polyesterols and/or polyetherolsand/or polycarbonatediols are preferably used as (b2), particularlypreferably polyesterdiols, for example polycaprolactone, and/orpolyetherpolyols, preferably polyetherdiols, for example those based onethylene oxide, propylene oxide and/or butylene oxide, preferablypolypropylene glycol, in particular polyetherols. Compounds to aresuitable for synthesizing a soft phase in the TPU are particularlypreferably used as (b2), for example copolyesters based on adipic acidand mixtures of 1,2-ethanediol and 1,4-butanediol, copolyesters based onadipic acid and mixtures of 1,4-butanediol and 1,6-hexanediol,polyesters based on adipic acid and 3-methyl-1,5-pentanediol and/orpolytetramethylene glycol (polytetrahydrofuran, PTHF), particularlypreferably copolyesters based on adipic acid and mixtures of1,2-ethanediol and 1,4-butanediol and/or polytetramethylene glycol(PTHF).

c) Compounds generally known as chain extenders, for example alkanediolsof 2 to 12, preferably 2, 3, 4 or 6, carbon atoms, can be used as diols(c), it also being possible to use mixtures of said compounds. Examplesare the following compounds: ethane-1,2-diol, propane-1,3-diol,hexane-1,6-diol and butane-1,4-diol.

d) Suitable catalysts which in particular accelerate the reactionbetween the NCO groups of the diisocyanates (a) and the hydroxyl groupsof the components (b2) and (b1) are the conventional tertiary aminesknown from the prior art, e.g. triethylamine, dimethylcyclohexylamine,N-methylmorpholine, N,N′-dimethylpiperazine,2-(dimethylaminoethoxy)ethanol, diazabicyclo[2.2.2]octane and the like,and in particular organic metal compounds, such as titanic acid esters.Apart from the reaction in step (i), the catalysts are usually used inamounts of from 0.0001 to 5 parts by weight per 100 parts by weight ofpolyhydroxy compound (b).

Suitable catalysts which accelerate the degradation reaction of thepreferably high molecular weight, preferably semicrystalline,thermoplastic polyesters with the component (c) are in particularorganic metal compounds, such as titanic acid esters, e.g. tetrabutylorthotitanate, iron compounds, e.g. iron(III) acetylacetonate, tincompounds, e.g. tin diacetate, tin dioctanoate, tin dilaurate or thedialkyltin salts of aliphatic carboxylic acids, such as dibutyltindiacetate, dibutyltin dilaurate or the like.

e) In addition to catalysts, conventional assistants (e) may also beadded to the components (a) and (b2). Examples are surface-activesubstances, flameproofing agents, antistatic agents, nucleating agents,lubricants and mold release agents, dyes and pigments, inhibitors,hydrolysis stabilizers, light stabilizers, heat stabilizers,antioxidants or stabilizers for preventing discoloration, agents forprotecting from microbial degradation, inorganic and/or organic fillers,reinforcing materials and plasticizers.

Further information concerning the abovementioned assistants is to befound in the technical literature.

Mixtures containing the novel thermoplastic polyurethanes and at leastone further thermoplastic material, for example polyolefins, polyester,polyamide, polyoxymethylene, polystyrene and/or styrene copolymers, arefurthermore according to the invention.

The advantages according to the invention are to be described withreference to the examples below.

EXAMPLES

The preparation of examples 1 to 21 described below was carried out in atwin-screw extruder of type ZSK 58 from Werner & Pfleiderer. The lengthof the extruder process part was 12 barrels and the length of thebarrels themselves was 4 times the screw diameter. The screw dischargefrom the extruder was carried out by means of a gear pump; thegranulation was effected in a conventional underwater granulation means.The resulting granules were then dried in a fluidized-bed dryer at from60 to 100° C. and in residence times of from 5 to 10 minutes to watercontents of <0.03% and then heated for 15 hours at 80° C.

The temperatures of extruder barrel 1 was 260° C., that of barrels 2-4was 250° C., that of barrel 5 was 240° C., that of barrels 6-12,including the melt discharge means, was 230° C. Under these conditions,the melt temperature of 220-230° C. resulted in the case of a throughputof about 200 kg/h and a speed of 200 rpm.

The semicrystalline, high molecular weight polyester used was acommercial polybutylene terephthalate (Ultradur® B 4500/BASFAktiengesellschaft), the low molecular weight diol used for degradingthe high molecular weight PBT was 1,4-butanediol and the aromaticdiisocyanate used was 4,4′-diisocyanatodiphenylmethane (MDI). Thepolydiols (PDO) used are described and characterized in table 1.

TABLE 1 Number av. mol. weight OH number Designation Composition Mn(g/mol) (mg KOH/1 g) PD0 1 Polyester of adipic acid, 2000 56.1 ethyleneglycol and 1,4- butanediol (molar ratio 1:1) PD0 2 Polyester of adipicacid, 2000 56.1 1,4-butanediol and 1,6- hexanediol (molar ratio 2:1) PD03 Polyester of adipic acid and 2000 56.1 3-methyl-1,5-pentanediol PD0 4Polyetherdiol based on 1000 112.2 polytetramethylene glycol

In example 1, the degradation of the Ultradur® B 4500 by 1,4-butanediolis described and the degradation products are characterized.

Ultradur® granules were metered continuously into the barrel 1 of thetwin-screw extruder, 1,4-butanediol together with tin dioctanoate as acatalyst for accelerating the degradation was metered into barrel 3 andmelt samples were taken from the opened barrel 5. The residence time ofthe melt (barrels 1-5) was about 44 seconds.

TABLE 2 ULTRADUR ® 1,4-Butanediol Tin dioctanoate Sample No. B 4500 kg/hkg/h g/h 1 40 0 0 2 40 1.20 4.0 3 40 1.80 4.0 4 40 2.40 4.0

For the determination of unconverted 1,4-butanediol, in each case 10 gof melt sample were powdered and then suspended in 30 g of isopropanoland stirred for 48 hours at room temperature for complete extraction ofthe butanediol. In the isopropanol solution, butanediol was determinedby gas chromatography. The insoluble fraction was filtered off, washedwith isopropanol and completely dried for several hours at 100° C. Thefollowing determinations were carried out on these extracted samples:

-   Viscosity number VN: A solution viscosity (m/l/g) of 0.5% strength    solution in phenol/chlorobenzene (1:1) at 25° C., measured using an    Ubbelohde viscometer-   Terminal group analysis: Dissolution in dichlorobenzene at 190° C.,    reaction with acetic anhydride and titration with 0.1 nNaOH solution-   GPC analysis: Eluent hexafluoroisopropanol +0.5% of potassium    trifluoroacetate, calibration with PMMA standards having a narrow    molecular weight distribution

TABLE 3 Content of Viscosity un-converted number Terminal groups Mnvalues butanediol VN Hydroxyl Acid from terminal from Sample No. (% bywt.) (ml/g) mmol/kg mmol/kg groups GPC 1 — 101 60.6 32.1 21600 16800 20.29 26.7 485 16.0 4000 3700 3 0.75 19.6 675 17.8 2900 2700 4 0.85 16.0848 21.4 2300 2200

The values in table 3 show that, in the novel process, the highmolecular weight polybutylene terephthalate can be degraded within theshort residence time to give polyester chains having substantiallyterminal hydroxyl groups and Mn values of from 2 000 to 4 000.

Examples 2 to 4 below describe how samples no. 2, 3 and 4 are furtherreacted according to the invention by adding polyesterdiol, MDI and tindioctanoate in barrel 5 of the twin-screw extruder.

TABLE 4 Molar Ultradur ® Tin dioctanoate Polyesterdiol ratio Example B4500 Butanediol Barrel 3 Barrel 5 PD02 MDI MDI/ No. kg/h kg/h g/h g/hkg/h kg/h (BD0 + PD02) 2 40 1.20 4.0 4.0 128.7 20.80 1.07 3 40 1.80 4.04.0 128.7 22.58 1.07 4 40 2.40 14.0 4.0 128.7 24.36 1.07 5 40 — — 4.0128.7 17.23 1.07 BD0 = Butanediol

In example 5 not according to the invention, Ultradur B 4500 was reactedwith PDO 2 and MDI without degradation by butanediol but under otherwiseidentical reaction conditions. In contrast to the visually clear andsingle-phase melts from examples 2 to 4, the melt according to example 5was opaque white, nontransparent and two-phase. After a run time of onlya few minutes, agglomeration of the extremely tacky granular particlesoccurred in the underwater granulation means and the experiment had tobe terminated. The product obtained up to then could not be processed byinjection molding. For comparative measurements, 2 mm thick test plateswere produced by pressing at about 190-200° C.

For the determination of the mechanical properties, the experimentalproducts were processed in a conventional manner by injection molding togive test specimens, which were heated for 20 hours at 100° C. beforethe test.

The tests were carried out under the following conditions:

Hardness: Shore A or Shore D, measured according to DIN 53505 TS:Tensile strength (MPa), measured according to DIN 53504 EB: Elongationat break (%), measured according to DIN 53504 TPS: Tear propagationstrength (N/mm), measured according to DIN 53515 Abrasion: Abrasion(mm3), measured according to DIN 53516 DSC values: Measured using a DSC7 apparatus from Perkin-Elmer and evaluated according to ISO 11357-3;Heating and cooling rates: 20_K/min. TM: Melting peak maximum (° C.)from the 2nd heating curve TKmax: Crystallization peak maximum (° C.)from the cooling curve

These conditions apply to examples 2 to 5 as well as to all examplesbelow.

TABLE 5 Ex- am- ple DSC values No. Hardness TS EB TPS Abrasion VN TMTKmax 2 67 A 19 850 41 57 329 209 165 3 71 A 23 880 50 47 328 196 134 473 A 25 840 51 47 337 186 119 5 58 A 8 800 10 >500 222 212 159

The values of the novel experimental products (examples 24) exhibit anexcellent property level, in particular with regard to thesolidification behavior in injection molding.

The values of example 5 not according to the invention show that it ismerely a physical mixture of a high molecular weight PBT with a highmolecular weight polyurethane soft phase, resulting not only in theextreme tack but also in the low tensile strength, low tear propagationstrength and extremely high abrasion.

In examples 6 to 9 below, it is intended to show that products having ahardness of from Shore 44 D to 75 D can be prepared by the novelprocess.

TABLE 6 Tin Ultradur ® dioctanoate Polyesterdiol Molar ratio Example B4500 Butanediol Barrel 3 Barrel 5 PDO2 MDI MDI/ No. kg/h kg/h g/h g/hkg/h kg/h (BD0 + PD02) 6 65.7 3.30 4.0 4.0 56.0 17.1 1.06 7 75.0 4.504.0 4.0 43.7 19.0 1.06 8 87.0 5.22 4.0 4.0 30.60 19.43 1.06 9 99.0 5.944.0 4.0 19.40 20.06 1.06

In addition to the substances stated in table 6, 1.45 kg/h of a powdermixture consisting of 25% of a finely divided talc (talc IT extra fromOmya), 25% of an antioxidant (Irganox® 1010 from Ciba-Geigy) and 50% ofa lubricant and mold release agent (Uniwax 1760 from Uniqema) were addedto barrel 8 of the twin-screw extruder via a laterally mounted screwmetering apparatus. The total throughput was then 144-146 kg/h.

TABLE 7 Ex- ample Hard- DSC values No. ness TS EB TPS Abrasion VN TMTKmax 6 44 D 32 590 112 15 271 190 140 7 54 D 38 410 151 18 249 189 1428 66 D 49 440 183 16 241 193 150 9 75 D 45 430 251 20 229 195 155

In examples 10 to 17 below, it is intended to show that products havinga hardness of from Shore 50 A to 80 A can be prepared by the novelprocess.

TABLE 8 Ultradur ® Tin dioctanoate Polyesterdiol B 4500 ButanediolBarrel 3 Barrel 5 PD01 MDI Molar ratio Example No. kg/h kg/h g/h G/hkg/h kg/h MDI/(BD0 + PD01) 10 20.0 1.20 4.0 4.0 146.9 24.24 1.116 1127.0 1.62 4.0 4.0 139.3 24.48 1.116 12 33.0 1.98 4.0 4.0 132.7 24.661.116 13 40.0 2.40 4.0 4.0 125.0 24.90 1.116

TABLE 9 Ultradur ® Tin dioctanoate Polyesterdiol Polyesterdiol Molarratio B 4500 Butanediol Barrel 3 Barrel 5 PD02 PD03 MDI MDI Example No.kg/h kg/h g/h g/h kg/h kg/h kg/h (BD0 + PD02 + PD03) 14 22.0 1.10 4.04.0 118.2 29.5 23.05 1.07 15 27.5 1.38 4.0 4.0 114.1 28.5 23.20 1.07 1633.0 1.65 4.0 4.0 109.2 27.3 23.18 1.07 17 36.5 1.86 4.0 4.0 106.4 26.623.33 1.07

In addition to the substances stated in tables B and 9, 2.00 kg/h of apowder mixture which has been described above in the case of examples 6to 9 were introduced into barrel 8 of the twin-screw extruder.

TABLE 10 Exam- Hard- DSC values ple No. ness TS EB TPS Abrasion VN TMTKmax 10 57 A 23 880 41 36 461 200 155 11 65 A 25 820 46 35 476 195 14012 71 A 23 850 53 33 472 200 150 13 77 A 31 860 62 35 458 197 144 14 52A 19 1240 24 104 387 195 139 15 56 A 18 1330 31 82 354 198 145 16 65 A26 1060 37 68 361 201 153 17 69 A 28 1080 41 68 348 197 155

In addition to good mechanical properties, the products according toexamples 10 to 17 show pronounced and very good solidification andcrystallization behavior which has a very positive effect on theprocessing behavior in injection molding and in extrusion, as will beshown below.

Examples 14 to 17 demonstrate that mixtures of polyesterdiols havingdifferent chemical structures can also be used in the novel process.This is sometimes important for suppressing subsequent crystallizationof the originally amorphous polyurethane soft phase and hence subsequenthardening during storage of the products

In addition to polyesterdiols, polyetherdiols orpolyesterdiol/polyetherdiol mixtures can also be used in the novelprocess, as will be explained with reference to examples 18 to 20.

TABLE 11 Ultradur ® Tin dioctanoate Polyesterdiol B 4500 ButanediolBarrel 3 Barrel 5 PD04 MDI Molar ratio Example No. kg/h kg/h g/h g/hkg/h kg/h MDI/(BD0 + PD04) 18 34.0 2.76 4.0 4.0 118.2 39.48 1.06 19 50.04.02 4.0 4.0 101.6 38.79 1.06 20 70.0 5.64 4.0 4.0 80.74 38.02 1.06

In addition to the substances stated in table 11, 2.00 kg/h of a powdermixture as described in the case of examples 6 to 9 were introduced intobarrel 8 of the twin-screw extruder

TABLE 12 Exam- Hard- DSC value ple No. ness TS EB TPS Abrasion VN TMTKmax 18 70 A 40 710 38 30 1603 178 71 19 80 A 43 610 64 27 1282 176 7520 90 A 50 470 74 30 640 180 80

In example 21 below, it is intended to show that a commercialpolyethylene terephthalate (polyester type RT 51 from Kosa) can bereacted according to the novel process.

TABLE 13 PET Tin dioctanoate Polyesterdiol Polyesterdiol RT 51Butanediol Barrel 3 Barrel 5 PD02 PD03 MDI Molar ratio MDI/ Example No.kg/h kg/h g/h g/h kg/h kg/h kg/h (BD0 + PD02 + PD03) 21 36.5 2.92 12.04.0 105.4 26.3 25.33 1.03

Owing to the higher melting range of polyethylene terephthalate, thetemperature profile of the twin-screw extruder was changed in thefollowing manner:

Barrels 1 to 4: 270° C. Barrel 5: 260° C. Barrels 6 to 12: 250° C. Meltdischarge means: 230° C.

In addition to the substances stated in table 13, 2.00 kg/h of a powdermixture as described in the case of examples 6 to 9 were introduced intobarrel 8 of the twin-screw extruder.

TABLE 14 Exam- Hard- DSC values ple No. ness TS EB TPS Abrasion VN TMTKmax 21 68 A 15 960 24 120 230 238 196

In examples 22 to 24 below, it is intended to show that an aliphaticdiisocyanate/hexamethylene 1,6-diisocyanate (HDI) can be reactedaccording to the novel process.

TABLE 15 Ultradur ® Tin dioctanoate Polyesterdiol B 4500 ButanediolBarrel 3 Barrel 5 PD02 HDI Molar ratio Example No. kg/h kg/h g/h g/hkg/h kg/h HDI/(BD0 + PD02) 22 37.5 2.25 4.0 12.0 95.8 12.38 1.01 23 45.02.70 4.0 12.0 87.7 12.53 1.01 24 52.5 3.15 4.0 12.0 79.5 12.69 1.01

TABLE 16 Exam- Hard- DSC values ple No. ness TS EB TPS Abrasion VN TMTKmax 22 79 A 13 950 41 100 150 179 71 23 84 A 15 880 50 52 163 179 6824 89 A 19 820 60 41 148 182 63

The present examples 2 to 24 show that block copolymers which differfrom the commercial thermoplastic polyurethanes in that the customaryhard phase segment, consisting of butanediol/MDI units, was exchangedfor semicrystalline, rapidly crystallizing, hard polyester segments canbe prepared by the novel process.

It is possible to prepare products which cover a hardness range of fromShore 50 A to Shore 75 D and have elastomeric behavior, in particularthe advantageous properties of the commercial thermoplasticpolyurethanes, such as high strengths in combination with highelongation at break, high tear propagation strengths and high abrasionresistances.

However, the advantage over the commercial thermoplastic polyurethanesis based on the narrow melting range and the tendency of thesemicrystalline polyester hard phase to crystallize, so thatproblem-free and rapid processing by injection molding and by extrusionis possible even in the case of very soft products having a hardness offrom Shore 50 A to Shore 75 A.

These advantageous processing properties are to be explained in examples25 and 26 below.

DE-A 199 39 112 describes thermoplastic polyurethanes having a hardnessof from Shore 50 A to 75 A. The experimental products according toexamples 9, 10 and 11 of DE-A 199 39 112 are based on polyesterdiol PDO1, like the products according to examples 10, 11 and 12 of the presentinvention.

TABLE 17 Hardness DE-A 199 39 112 Example 9 73 A Example 10 66 A Example11 58 A According to the invention Example 10 57 A Example 11 65 AExample 12 71 A

Example 25 Processability by Injection Molding

The products mentioned in table 15 were processed on an injectionmolding machine, type ES 330/125 from Engel, under optimized conditionsto give a round disk having a diameter of 120 mm and a thickness of 2mm. Optimized conditions mean that, for each individual product, theinjection conditions, the temperature profile of the injection unit andthe hot runner, and the tool surface temperatures were varied andoptimized until a homogeneous, planar round disk having gooddemoldability and dimensional stability resulted. The cycle timesdetermined after such a process represent a good comparative standardfor rating the processability, shorter cycle times being positivelyrated.

TABLE 18 According to the DEA 199 39 112 invention Examples Examples 1110 9 10 11 12 Hardness (Shore) 58 A 66 A 73 A 57 A 65 A 71 A Cycle time(sec) 100 90 75 45 40 35

Example 26 Processability by Extrusion (Production of Blown Films)

The products described in table 15 were processed to give blown films ona Brabender laboratory unit comprising melting extruder, film blowinghead and take-off apparatus. After appropriate optimization of theextruder temperature profile, of the annular gap width of the filmblowing head, of the blow air flow rate and of the take-oft speed,satisfactory blown films could be produced and wound in all cases. Incase of the products according to DE-A 199 39 112, however, thetransparent blown films stuck together to such an extent during windingthat the spool could no longer be unwound later on without destructionof the film. Owing to the strong adhesion, it was also impossible toblow up the tubular film.

The novel products on the other hand gave slightly opaque tubular filmswithout any tendency to stick. The spools were always readily unwindablelater on and the tubular film itself could be blown up without problems.There were no detectable differences between the individual hardnessgradations with respect to tendencies to adhere.

We claim:
 1. A thermoplastic polyurethane obtainable by reacting (a)isocyanates with (b1) polyesterdiols having a melting point greater than150° C., (b2) polyetherdiols and/or polyester diols, each having amelting point of less than 150° C. and a molecular weight of from 501 to8 000 g/mol, and, if required, (c) diols having a molecular weight offrom 62 to 500 g/mol.
 2. A thermoplastic polyurethane as claimed inclaim 1, wherein the molar ratio of the diols (c) having a molecularweight of from 62 to 500 g/mol to the component (b2) is less than 0.2.3. A thermoplastic polyurethane as claimed in claim 1, wherein thepolyesterdiols (b1) have the following structural unit

where R₁ is a carbon skeleton of 2 to 15 carbon atoms, R₂ is an alkylenegroup of 2 to 8 carbon atoms, R₃ is an alkylene group of 2 to 8 carbonatoms and X is an integer from 5 to
 30. 4. A thermoplastic polyurethaneas claimed in claim 1, wherein the polyesterdiol (b1) has a molecularweight of from 1 000 to 5 000 g/mol.
 5. A process for the preparation ofthermoplastic polyurethanes, wherein (i) a thermoplastic polyester isreacted with a diol (c) and then (ii)the reaction product of (i)containing (b1) polyesterdiol having a melting point greater than 150°C. and, if required, (c) diol together with (b2) polyetherdiols and/orpolyesterdiols, each having a melting point of less than 150° C. and amolecular weight of from 501 to 8 000 g/mol and, if required, further(c) diols having a molecular weight of from 62 to 500 g/mol are reactedwith a) isocyanate, in the presence or absence of (d) catalysts and/or(e) assistants,
 6. A process as claimed in claim 5, wherein the molarratio of the (c) diols having a molecular weight of from 62 to 500 g/molto the component (b2) in the reaction (ii) is less than 0.2.
 7. Aprocess as claimed in claim 5, wherein the thermoplastic polyester has amolecular weight of from 15 000 to 40 000 g/mol.
 8. A process as claimedin claim 5, wherein the thermoplastic polyester used is a polyalkyleneterephthalate and/or a poly-L-lactic acid.
 9. A process as claimed inclaim 5, wherein the thermoplastic polyester is melted at from 180 to270° C. and the reaction (i) with the diol (c) is carried out at from240 to 280° C.
 10. A process as claimed in claim 5, wherein the reactionof the thermoplastic polyester with the diol (c) is carried out in thepresence of a catalyst.
 11. A process as claimed in claim 5, wherein thepolyesterdiol (b1) as a reaction product from (i) has a molecular weightof from 1 000 to 5 000 g/mol.
 12. A process as claimed in claim 5,wherein butane-1,4-diol and/or ethane-1,2-diol are used as diol (c) in(i) and, if required, in (ii)
 13. A process as claimed in claim 5,wherein the reactions (i) and (ii) are carried out in a reactionextruder.
 14. A process as claimed in claim 13, wherein the reactionextruder has neutral and/or backward-conveying kneading blocks andbackward-conveying elements in the region in which the thermoplasticpolyester is melted and screw mixing elements, toothed disks and/ortoothed mixing elements in combination with backward-conveying elementsin the region in which the thermoplastic polyester is reacted with thediol.
 15. A process as claimed in claim 5, wherein, in the reaction(ii), the ratio of the isocyanate groups to the hydroxyl groups is from1:1 to 1.2:1.
 16. A thermoplastic polyurethane obtainable by a processas claimed in any of claims 5 to
 15. 17. A thermoplastic polyurethane asclaimed in claim 16, which has a hardness range of from Shore 45 A toShore 78 D.
 18. A film, shaped article, roller, fiber or cladding in anautomobile, hose, cable plug, bellows, trailing cable, cable sheath,seal, belt or damping element containing a thermoplastic polyurethane asclaimed in claim 16 or
 17. 19. A mixture containing a thermoplasticpolyurethane as claimed in any of claims 1 to 4, 16 or 17 and at leastone further thermoplastic material.